Although cellular responses to genotoxic (DNA damage) or ER stress are complex, they are vital for cellular homeostasis. Aberrations in cellular responses to these stresses can have profound effects giving rise to major abnormalities including cancer, cardiovascular anomalies, diabetes and neurodegenerative disorders. This application is to characterize a novel gene that we have named BBEL1 (Bax and Bak interacting E3 Ligase 1). BBEL1 encodes a novel stress-regulated E3 ubiquitin ligase that localizes to mitochondria. BBEL1 inhibits DNA damage-induced apoptosis and interacts with the pro-apoptotic Bax and Bak. We hypothesize that BBEL1 is a novel mitochondrial anti-apoptotic E3 ubiquitin ligase that mediates its anti-apoptotic effects by inhibiting Bax and Bak and thus, a key component in the cellular stress response pathways. We are proposing three specific aims to further characterize BBEL1. Specific Aim 1 is to determine the topology and localization of BBEL1. Specific Aim 2 is to investigate the molecular basis for Bax and Bak interactions with BBEL1. Specific Aim 3 is to perform structural functional characterization of BBEL1. Proposed studies are critical initial steps to characterize BBEL1 and to lay the groundwork for further in-depth studies aiming to determine the exact function of this novel ubiquitin ligase particularly in context to toxicology and pathobiology of human diseases. PUBLIC HEALTH RELEVANCE: Cellular responses to DNA damage and other types of stresses are complex yet very vital for cellular wellbeing. Defects in cellular responses to these stresses can have profound effects giving rise to major abnormalities including cancer, cardiovascular anomalies, diabetes and neurodegenerative disorders. Here we propose to characterize a novel gene BBEL1 that encodes a novel stress-regulated E3 ubiquitin ligase. BBEL1 appears to be a key component of cellular stress response pathways as it inhibits DNA damage-induced apoptosis and interacts with pro-apoptotic proteins. Proposed studies are critical initial steps to characterize BBEL1 and to lay the groundwork for further in-depth studies aiming to determine the exact function of this novel ubiquitin ligase particularly in context to toxicology and pathobiology of human diseases.